Abstract Inadequate physical activity and poor diet quality contribute to the high overweight/obesity (OW/O) prevalence in adolescents, aged 12-19 years, indicating a need to intervene at or before age 12. Compared with other adolescents, underserved (minority; low socioeconomic status) adolescents in urban areas exhibit more unhealthy behaviors that increase their risk for obesity and related cardiovascular disease (CVD). Guided by Self-Determination Theory and the Information-Motivation-Behavioral Skills Model, the novel 16-week Guys/Girls Opt for Activities for Life (GOAL) intervention includes 3 components: 1) After-school GOAL Club: 26 120-minute events (2 days/week) for boys and girls that incorporate physical activity and healthy eating and cooking; 2) Three parent-adolescent dyad meetings to empower dyads about physical activity and healthy eating and cooking; and 3) GOAL social networking website so parents can motivate each other to help their adolescents increase physical activity and diet quality. The purpose of this 5-yr group randomized trial (unit of assignment is school) is to evaluate the effect of GOAL on decreasing CVD risk factors (high % body fat, OW/O, low CV fitness), improving quality of life (QOL); and increasing motivation, self-efficacy, and social support to increase MVPA and diet quality among underserved adolescents (5th?7th grade) having BMI z-score ?0. The long-term goal is to improve the CV health of underserved adolescents to decrease health disparities, a major priority of NHLBI. Eighteen schools will be randomly assigned to receive either GOAL (n=9) or usual school offerings control (n=9) condition. Forty dyads of boys (n=20) and girls (n=20) in each school and one parent per adolescent who is willing to serve as a support person will be enrolled (720 dyads total). Analysis will be based on the intention-to-treat principle. Aims are to evaluate effect of the GOAL intervention, compared to control, on: (1) Improving % body fat (primary outcome) by ?2.5% between intervention and control adolescents with a BMI z-score ?0 from baseline (0 months) to 4 months (immediate post-intervention) and to 13 months post-baseline (9-mon. F/U); (2) Increasing secondary proximal outcomes among adolescents: MVPA (via accelerometers; min/hr) and diet quality (healthy eating index based on 3 24-hr dietary recalls) from 0 to 4 months; (3) Improving secondary distal outcomes: CV fitness (Progressive Aerobic CV Endurance Run, [15- or 20-m shuttle run]) from 0 to 4 months; and BMI, OW/O percentage, & QOL from 0 to 4 months and to 13 months; and (4) Increasing social support, self-efficacy, and motivation with evaluation of any mediating effect on adolescent PA and diet quality. An exploratory aim (parents) is to evaluate any effect of GOAL, compared to control, on: (1) Improving parents? perceived family nutrition and PA, MVPA (via accelerometers), and diet quality (fruit-vegetable-fiber screener) from 0 to 4 months; and (2) Reducing parents? % body fat and BMI from 0 to 4 months and to 13 months.